Steel having a high yield point and a good notch toughness



Patented Nov. J 29, 1932 UNITED STATES PATENT OFFICE f ADOLF KLINKENBERG, OI 'WITTERAUCKE, NEAR HEB-DECKE, GERMANY, ASSIGNOR TO THE FIRM VEBEINIGTE STAHLWEBKE AKTIENGESELLSCHAFT, OF DUSSELDORF,

GERMANY STEEL HAVING A. HIGH YIELD POINT AND A GOOD NOTGH TOUGHNESS No Drawing. Application filed January 29, 1931, Serial No. 512,194, and in Germany January 8, 1930.

As is well known the physical properties of steel are influenced by phosphorus to quite a considerable degree in such a way that by an addition of about 0.1% of phosphorus the yield oint as well as the tensile strength are consi erably increased, the capability of chan ing t e form, particularly the notch toug ness very considerably decreased. Therefore, phosphorus as an unquestioned generator of cold-shortness belongs to the undesirable elements in the metallurgy of iron and generally speaking is held in decidedly low repute (cf. Oberhofier: Das technische Eisen, page 206). It is for this reason that the alloying value of phosphorus is made use of to a very limited extent only in spite of the influence of phosphorus on the yield point and tensile strength that in itself is a favorable one. Thus for parts of minor importance, such as pressed nuts, bicycle parts etc. phosphorus bearing steels are used to a limited extent since they have a clean surface after cold-working. In a similar way the action of phosphorus is utilized for the purpose of increasing the capabilityofbeing Worked by cutting tools of the free cutting steel. Thus the use of phosphorus bearing steels is relatively limited to fields wherein the stresses are small and at the same time the breaking safety factor is of minor importance. For use in higher stressed structural material, for example in the construction of bridges, Vehicles or machines the phosphorus content of the steel has heretofore been kept relatively low considering the danger of cold-shortness. Thus in the standerd steels the phosphorus content is limited to a maximum amount of According to the invention one succeeds in producing phosphorus bearing steels having a high yield point and tensile strength without causing the heretofore unavoidable great reduction in toughness to take place as a result of the phosphorus content by alloying a certain percentage of copper with the phosintercepting the melt.

phorus bearing steels, which are poor in caron. It is true that with increasing tensile strength a corresponding decrease in the strain values takes place, butthe notch toughness of the phosphorus-copper steels which are the subject of the invention suflices for the practical purposes of the erection of large steel structures.

The carbon and phosphorus contents have a certam reciprocal action and this is the reason why it is'to be preferred to fix the upper limit of the carbon content at about 0.3%. Preferably the phosphorus content is added already in starting the meltby suitably com posing the charge and is maintained, particularly in the basic Bessemer process, by In a'similar way the copper content may also originate from the charge or it may be added to the finished melt in solid or liquid form. The upper limit of the copper content is about 1%. Further- -more it has proved advantageous to deoxidize the melt in known manner for the purpose of avoiding segregation by means ofthe .usual deoxidizers, such as silicon, manganese or aluminum.

, By combining suitable proportions of phosphorus and copper new steels are produced for a great variety of uses in connection with the erection of large steel structures. In order to illustrate the excellent tensile prop erties of such steels the following examples are given:

(-1) A steel of the following composition: 0.10% o, 0.1% Si, 0.50%Mn, 0.14% P, 0.05% S, 0.64% Cu, had the following physical properties: a

(2) A steel of the same composition yet with 0.22% P had the following physical properties:

5 Exten- Con- Yield i S!) trac- Yield Point X100 Notch k p/oint 2 regs 610 tion Tensilestrength :glggt/mess g. mm. per per per cen g. cm.

cent cent The phosphorus-copper steels, apart from good static properties have also a high fatigue limit, thus with the steel of Example (1) a m fatigue limit of: 34 kg/mm has been ascertained on the rotating beam testing machine. Furthermore, by increasing the phosphorus content the resistance to wear is practically considerably increased and the tendency to 20 rust decreased.

What I claim and desire to secure by Letters Patent of the United States is:

1. A steel having a high yield point and a good notch toughness, a low carbon content rom about 0.1% to 0.3%, a small amount of sulphur not exceeding 0.05%, a phosphorus content ranging between 0.1 and 0.4% and a copper content of between 0.1 and 1% and the remainder substantially iron.

2. A steel having a yield'point ranging from 39.5 to 44.5 kg. per sq. mm. and a notch toughness ranging from 10 to 13 mkg. per sq. cm., a carbon content from about 0.01% to 0.3%, a phosphorus content ranging from 0.1

to 0.4%, a small amount of sulphur not exceeding 0.05% and a copper content of 0.1 to 1% and the remainder substantially iron.

3. A steel of the following composition: 0.1% carbon, 0.1% silicon, 0.5% manganese,

40 0.14% phosphorus, 0.05% sulphur, 0.64% copper and the remainder substantially iron.

In testimon whereof I aflix my signature.

OLF KLINKENBERG. 

